1. Field of the Invention
The present invention relates to a wire-cut, electric discharge machining method for cutting a workpiece into one or more closed loop configurations such as a punch, die or the like through the use of a wire-cut, electric discharge machine provided with an automatic wire feed mechanism. More particularly, the invention pertains to a wire-cut, electric discharge machining method which permits further machining even in the case of a wire electrode being broken during machining, and which makes the machining operation less troublesome.
2. Description of the Prior Art
In recent years, a workpiece has often been cut into a closed loop configuration such as a punch, die or the like through the use of a wire-cut, electric discharge machine equipped with an automatic wire feed mechanism for automatically reinstalling a wire electrode on a running system.
FIG. 1 is explanatory of a conventional wire-cut, electric discharge machining method for cutting out a punch from a workpiece by the employment of the wire-cut, electric discharge machine provided with the automatic wire feed mechanism. In FIG. 1, reference numeral 1 indicates a workpiece; 2 designates a machining start hole; 3 identifies a of the workpiece left uncut; 4 denotes a portion of the punch; and 5 represents adhesive materials.
According to the prior art method, a wire electrode (not shown) is first inserted into the machining start hole 2 made in the workpiece 1, and electric discharge machining is performed along a route (A.fwdarw.B.fwdarw.C) and is stopped at the point C, leaving the part 3 uncut. The reason for leaving the part 3 uncut is to prevent the punch portion 4 from falling off the workpiece 1 and, avoiding breakage of the wire electrode. Next, the punch portion 4 is fixed to the workpiece 1 using the adhesive binder as indicated by 5 in FIG. 1 and then electric discharge machining is carried out along the broken-line route (C.fwdarw.B) to cut the part remaining uncut portion 3, obtaining a punch.
With the conventional method described above, if the wire electrode is broken in the course of electric discharge machining, the wire electrode is reinstalled on the running system and the machining operation is resumed in the manner described below.
In the event that the wire electrode is broken during electric discharge machining, the wire electrode and the workpiece 1 are moved relative to each other to the same positions as they were placed at the start of the machining operation and the wire electrode is inserted by the automatic wire feed mechanism into the machining start hole 2 for reinsallment on the running system. Next, the wire electrode and the workpiece 1 are moved relative to each other along the machining route where the electric discharge machining operation has already been conducted. After the wire electrode and the workpiece 1 have thus been brought to the same relative positions as when the wire electrode was broken, the electric discharge machining operation is restarted.
In the case where the wire electrode is broken during machining along the route (A.fwdarw.B.fwdarw.C), the machining operation can be automatically resumed by the abovesaid method, but in the case of breakage of the wire electrode during machining along the route (C.fwdarw.B), no further machining can be carried out. That is to say, since the punched portion 4 is fixed to the workpiece 1 as indicated by 5 in FIG. 1 before the machining operation along the route (B.fwdarw.C), the presence of the fixed portions 5 makes it impossible to move the wire electrode and the workpiece 1 relative to each other along the machining route where the electric discharge machining has already been effected. Problem can be avoided in the following manner. When the wire electrode has been brought to a position immediately before one of the fixed portions 5, the relative movement of the workpiece 1 and the wire electrode is stopped; the adhesive material is removed; the wire electrode and the workpiece 1 are moved relative to each other by a fixed distance; the punched portions is fixed again to the workpiece 1 using the adhesive binder; the wire electrode is brought to a position immediately before the other fixed portion 5; and the abovesaid operations are repeated. This is, however, very time-consuming and troublesome.
FIG. 2 is explanatory of cutting a workpiece into a plurality of punches by the conventional wire-cut, electric discharge machining method using the wire-cut, electric discharge machine provided with the automatic wire feed mechanism. In FIG. 2, reference numeral 6 indicates a workpiece; 7, 9 and 11 designate machining start holes; 8, 10 and 12 identify parts remaining uncut; 13 to 15 denote punch portions; and, 16a to 16f represent adhesive materials.
At first, a wire electrode (not shown) is inserted into the machining start hole 7 and electric discharge machining is performed along the route (A.fwdarw.B.fwdarw.C) and, at the point C, the machining operation is stopped, leaving the part 8 uncut. Next, the punch portion 13 is fixed to the workpiece 6 using the adhesive material as indicated by 16a and 16b and then electric discharge machining is carried out along the broken-line route (C.fwdarw.B), thus cutting out the punch portion 13 from the workpiece 6.
After cutting out the punched portion 13 from the workpiece 6, the wire electrode is inserted by the automatic wire feed mechanism into the machining start hole 9 and, as described above, electric discharge machining is effected along the route (D.fwdarw.E.fwdarw.F); the part 10 is left uncut; the punched portion 14 is fixed to the workpiece 6 using the adhesive material as indicated by 16c and 16d; and then electric discharge machining takes place along the broken-line route (F.fwdarw.E), cutting out the punch portion 14 from the workpiece 6. The punch portion 15 is also cut out in the same manner as described above.
As described above, according to the prior art method, the punch portions are cut out from the workpiece 6 one by one; hence, this method is very troublesome in that the punch portions 13 to 15 have to be fixed to the workpiece 6 after electric discharge machining along the routes (A.fwdarw.B.fwdarw.C), (D.fwdarw.E.fwdarw.F) and (G.fwdarw.H.fwdarw.I), respectively. Moreover, if the wire electrode is broken during cutting off the parts left uncut 8, 10 and 12, no further machining can be effected as described previously.